The GOP cited that in their rule change for Supreme Court justices. Before it was limited only to lower courts.
The rule was in place after the GOP refused to hear any Obama nominees. It was warned back then that it will come back to bite them in the ass and sure enough it did.
The one thing not coded in the constitution though is how many justices sit on the Supreme Court. That is actually in the Judicial Act of 1869 which set the number of justices to 9. It had been as high as 10 previously. But there is nothing stopping them if they have the votes to create a bill allowing more justices to be on the court and start flooding the court with them.